Method and apparatus for mobility in wireless communication system

ABSTRACT

The present disclosure relates to method and apparatus for mobility wireless communications. According to an embodiment of the present disclosure, a method performed by a wireless device in a wireless communication system comprises: performing measurements to derive a cell quality; determining a set of candidate cells for a mobility based on the cell quality; selecting a mobility target cell from the set of candidate cells for the mobility based on a number of good beams and a number of detected beams; and performing the mobility to the mobility target cell.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present disclosure relates to method and apparatus for mobility wireless communications.

Related Art

3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.

Work has started in international telecommunication union (ITU) and 3GPP to develop requirements and specifications for new radio (NR) systems. 3GPP has to identify and develop the technology components needed for successfully standardizing the new RAT timely satisfying both the urgent market needs, and the more long-term requirements set forth by the ITU radio communication sector (ITU-R) international mobile telecommunications (IMT)-2020 process. Further, the NR should be able to use any spectrum band ranging at least up to 100 GHz that may be made available for wireless communications even in a more distant future.

The NR targets a single technical framework addressing all usage scenarios, requirements and deployment scenarios including enhanced mobile broadband (eMBB), massive machine-type-communications (mMTC), ultra-reliable and low latency communications (URLLC), etc. The NR shall be inherently forward compatible.

In a wireless communication system, a wireless device and/or user equipment (UE) may move along cells/base stations deployed in a wide range of areas. To provide proper services to the wireless device, the network should manage a mobility of the wireless device, and the wireless device should perform a mobility to another cell according to the mobility management. It may be required for a UE to select a proper mobility target cell so that the UE can be provided with services with better quality.

SUMMARY OF THE DISCLOSURE Technical Problem

An aspect of the present disclosure is to provide method and apparatus for a mobility in a wireless communication system.

An aspect of the present disclosure is to provide method and apparatus for a mobility in multi-beam environment in a wireless communication system.

Another aspect of the present disclosure is to provide method and apparatus for selecting a mobility target cell based on multiple beams of neighbor cells in a wireless communication system.

Another aspect of the present disclosure is to provide method and apparatus for selecting a mobility target cell among candidate cells for mobility in a wireless communication system.

Another aspect of the present disclosure is to provide method and apparatus for determining candidate cells for mobility in a wireless communication system.

Technical Solution

According to an embodiment of the present disclosure, a method performed by a wireless device in a wireless communication system comprises: performing measurements to derive a cell quality; determining a set of candidate cells for a mobility based on the cell quality; selecting a mobility target cell from the set of candidate cells for the mobility based on a number of good beams and a number of detected beams; and performing the mobility to the mobility target cell.

According to an embodiment of the present disclosure, a wireless device in a wireless communication system comprises: a transceiver; a memory; and at least one processor operatively coupled to the transceiver and the memory, and configured to: perform measurements to derive a cell quality, determine a set of candidate cells for a mobility based on the cell quality, select a mobility target cell from the set of candidate cells for the mobility based on a number of good beams and a number of detected beams, and performing the mobility to the mobility target cell.

According to an embodiment of the present disclosure, a processor for a wireless device in a wireless communication system is configured to control the wireless device to perform operations comprising: performing measurements to derive a cell quality; determining a set of candidate cells for a mobility based on the cell quality; selecting a mobility target cell from the set of candidate cells for the mobility based on a number of good beams and a number of detected beams; and performing the mobility to the mobility target cell.

According to an embodiment of the present disclosure, a computer-readable medium having recorded thereon a program for performing each step of a method on a computer is provided. The method comprises: performing measurements to derive a cell quality; determining a set of candidate cells for a mobility based on the cell quality; selecting a mobility target cell from the set of candidate cells for the mobility based on a number of good beams and a number of detected beams; and performing the mobility to the mobility target cell.

Advantageous effect

The present disclosure can have various advantageous effects.

For example, a UE may consider a proportion of good beams instead of the number of good beams when the UE selects a mobility target cell among candidate cells for a mobility so that the UE can select more robust cell from a UE perspective. By selecting more robust cell, a rate of a mobility success can be increased and a signalling overhead caused by an unnecessary mobility can be avoided.

Advantageous effects which can be obtained through specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there may be a variety of technical effects that a person having ordinary skill in the related art can understand and/or derive from the present disclosure. Accordingly, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that may be understood or derived from the technical features of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows examples of 5G usage scenarios to which the technical features of the present disclosure can be applied.

FIG. 2 shows an example of a wireless communication system to which the technical features of the present disclosure can be applied.

FIG. 3 shows an example of a wireless communication system to which the technical features of the present disclosure can be applied.

FIG. 4 shows another example of a wireless communication system to which the technical features of the present disclosure can be applied.

FIG. 5 shows a block diagram of a user plane protocol stack to which the technical features of the present disclosure can be applied.

FIG. 6 shows a block diagram of a control plane protocol stack to which the technical features of the present disclosure can be applied.

FIG. 7 illustrates a frame structure in a 3GPP based wireless communication system.

FIG. 8 illustrates a data flow example in the 3GPP NR system.

FIG. 9 shows an example of a dual connectivity (DC) architecture to which technical features of the present disclosure can be applied.

FIG. 10 shows an example of handover procedure to which technical features of the present disclosure can be applied.

FIG. 11 shows an example of a conditional handover procedure to which technical features of the present disclosure can be applied.

FIG. 12 shows an example of a method for selecting a mobility target cell according to an embodiment of the present disclosure.

FIG. 13 shows an example of a good beam proportion for each candidate cell according to an embodiment of the present disclosure.

FIG. 14 shows an example of cell qualities of neighbour cells according to an embodiment of the present disclosure.

FIG. 15 shows a UE to implement an embodiment of the present disclosure.

FIG. 16 shows another example of a wireless communication system to which the technical features of the present disclosure can be applied.

FIG. 17 shows an example of an AI device to which the technical features of the present disclosure can be applied.

FIG. 18 shows an example of an AI system to which the technical features of the present disclosure can be applied.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The technical features described below may be used by a communication standard by the 3rd generation partnership project (3GPP) standardization organization, a communication standard by the institute of electrical and electronics engineers (IEEE), etc. For example, the communication standards by the 3GPP standardization organization include long-term evolution (LTE) and/or evolution of LTE systems. The evolution of LTE systems includes LTE-advanced (LTE-A), LTE-A Pro, and/or 5G new radio (NR). The communication standard by the IEEE standardization organization includes a wireless local area network (WLAN) system such as IEEE 802.11a/b/g/n/ac/ax. The above system uses various multiple access technologies such as orthogonal frequency division multiple access (OFDMA) and/or single carrier frequency division multiple access (SC-FDMA) for downlink (DL) and/or uplink (UL). For example, only OFDMA may be used for DL and only SC-FDMA may be used for UL. Alternatively, OFDMA and SC-FDMA may be used for DL and/or UL.

In the present disclosure, “A or B” may mean “only A”, “only B”, or “both A and B”. In other words, “A or B” in the present disclosure may be interpreted as “A and/or B”. For example, “A, B or C” in the present disclosure may mean “only A”, “only B”, “only C”, or “any combination of A, B and C”.

In the present disclosure, slash (/) or comma (,) may mean “and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B” may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C” may mean “A, B or C”.

In the present disclosure, “at least one of A and B” may mean “only A”, “only B” or “both A and B”. In addition, the expression “at least one of A or B” or “at least one of A and/or B” in the present disclosure may be interpreted as same as “at least one of A and B”.

In addition, in the present disclosure, “at least one of A, B and C” may mean “only A”, “only B”, “only C”, or “any combination of A, B and C”. In addition, “at least one of A, B or C” or “at least one of A, B and/or C” may mean “at least one of A, B and C”.

Also, parentheses used in the present disclosure may mean “for example”. In detail, when it is shown as “control information (PDCCH)”, “PDCCH” may be proposed as an example of “control information”. In other words, “control information” in the present disclosure is not limited to “PDCCH”, and “PDDCH” may be proposed as an example of “control information”. In addition, even when shown as “control information (i.e., PDCCH)”, “PDCCH” may be proposed as an example of “control information”.

Technical features that are separately described in one drawing in the present disclosure may be implemented separately or simultaneously.

The terms used throughout the disclosure can be defined as the followings:

‘Good beam’ refers to a beam whose beam quality is above a beam quality threshold. The beam quality threshold may be signalled/configured by a network to the UE via DCl/MAC CE/RRC signalling. Throughout the disclosure, the terms ‘RRC signalling’ and ‘higher layer signalling’ can be used inter-changeably. Good beam may also be referred to as significant/effective beam which may be candidate beam for communication.

‘Beam quality’ refers to a quality of a beam that can be obtained by measuring the beam or measuring a signal (e.g., reference signal such as synchronization signal block (SSB) or channel state information reference signal (CSI-RS)) transmitted through the beam. That is, a beam may correspond to an SSB and/or a CSI-RS. SSB may comprise a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a physical broadcast channel (PBCH). The SSB may also be referred to as SS/PBCH block. Beam quality may also be referred to as beam strength/signal quality/signal strength/RSRP/RSRQ/SINR/channel quality/channel state of the beam.

‘Cell quality’ refers to a quality of a cell that can be obtained by measuring the cell or measuring a signal (e.g., reference signal) transmitted from the cell. Cell quality may also be referred to as signal quality/signal strength/RSRP/RSRQ/SINR/channel quality/channel state of the cell. Cell quality of a cell may comprise cell ranking of the cell. Cell quality of a cell may be determined based on a beam quality of one or more good beams associated with the cell. For example, cell quality of a cell may be determined by averaging beam quality values of one or more good beams associated with the cell.

‘Mobility’ refers to a procedure for i)changing a PCell of a UE (i.e., handover or PCell change), ii)changing a PSCell of a UE (i.e., SN change or PSCell change), and/or iii)adding a PSCell for a UE (i.e., SN addition or PSCell addition). Therefore, the mobility may comprise at least one of a handover, an SN change or an SN addition. In other words, the mobility may comprise at least one of PCell change, PSCell change or PSCell addition. Throughout the disclosure, performing a mobility to a target cell may refer to applying a mobility command of the target cell or applying RRC reconfiguration parameters in the mobility command of the target cell. Further, RRC reconfiguration and RRC connection reconfiguration may be used interchangeably.

‘Conditional mobility’ refers to a mobility that is performed to a target cell which satisfies a triggering condition among a plurality of candidate target cells. Throughout the disclosure, performing a conditional mobility to a target cell may refer to applying a conditional mobility command of a target cell which satisfies a mobility condition for the target cell among a plurality of candidate target cells or applying RRC reconfiguration parameters in the conditional mobility command of the target cell which satisfies a mobility condition for the target cell among the plurality of candidate target cells.

‘Mobility condition for a target cell’ refers to a triggering condition for a mobility to the target cell. That is, the mobility condition for a target cell refers to a condition that should be satisfied for triggering a mobility to the target cell. Mobility condition may comprise at least one of an event, time-to-trigger (TTT), offset value, or threshold value(s). The mobility condition for an event may be satisfied if an entering condition for the event is satisfied for at least the TTT. For example, the entering condition for event A3 may be satisfied if a signal quality for a target cell is better than that for a source cell more than or equal to the offset value. For another example, the entering condition for event A4 may be satisfied if a signal quality for a target cell is better than a neighbor cell threshold. For another example, the entering condition for event A5 may be satisfied if a signal quality for a target cell is better than a neighbor cell threshold and a signal quality for a source cell is lower than a serving cell threshold.

Throughout the disclosure, the terms ‘radio access network (RAN) node’, ‘base station’, ‘eNB’, ‘gNB’ and ‘cell’ may be used interchangeably. Further, a UE may be a kind of a wireless device, and throughout the disclosure, the terms ‘UE’ and ‘wireless device’ may be used interchangeably.

The following drawings are created to explain specific embodiments of the present disclosure. The names of the specific devices or the names of the specific signals/messages/fields shown in the drawings are provided by way of example, and thus the technical features of the present disclosure are not limited to the specific names used in the following drawings.

FIG. 1 shows examples of 5G usage scenarios to which the technical features of the present disclosure can be applied.

The 5G usage scenarios shown in FIG. 1 are only exemplary, and the technical features of the present disclosure can be applied to other 5G usage scenarios which are not shown in FIG. 1.

Referring to FIG. 1, the three main requirements areas of 5G include (1) enhanced mobile broadband (eMBB) domain, (2) massive machine type communication (mMTC) area, and (3) ultra-reliable and low latency communications (URLLC) area. Some use cases may require multiple areas for optimization and, other use cases may only focus on only one key performance indicator (KPI). 5G is to support these various use cases in a flexible and reliable way.

eMBB focuses on across-the-board enhancements to the data rate, latency, user density, capacity and coverage of mobile broadband access. The eMBB aims ˜10 Gbps of throughput. eMBB far surpasses basic mobile Internet access and covers rich interactive work and media and entertainment applications in cloud and/or augmented reality. Data is one of the key drivers of 5G and may not be able to see dedicated voice services for the first time in the 5G era. In 5G, the voice is expected to be processed as an application simply using the data connection provided by the communication system. The main reason for the increased volume of traffic is an increase in the size of the content and an increase in the number of applications requiring high data rates. Streaming services (audio and video), interactive video and mobile Internet connectivity will become more common as more devices connect to the Internet. Many of these applications require always-on connectivity to push real-time information and notifications to the user. Cloud storage and applications are growing rapidly in mobile communication platforms, which can be applied to both work and entertainment. Cloud storage is a special use case that drives growth of uplink data rate. 5G is also used for remote tasks on the cloud and requires much lower end-to-end delay to maintain a good user experience when the tactile interface is used. In entertainment, for example, cloud games and video streaming are another key factor that increases the demand for mobile broadband capabilities. Entertainment is essential in smartphones and tablets anywhere, including high mobility environments such as trains, cars and airplanes. Another use case is augmented reality and information retrieval for entertainment. Here, augmented reality requires very low latency and instantaneous data amount.

mMTC is designed to enable communication between devices that are low-cost, massive in number and battery-driven, intended to support applications such as smart metering, logistics, and field and body sensors. mMTC aims ˜10 years on battery and/or ˜1 million devices/km2. mMTC allows seamless integration of embedded sensors in all areas and is one of the most widely used 5G applications. Potentially by 2020, internet-of-things (IoT) devices are expected to reach 20.4 billion. Industrial IoT is one of the areas where 5G plays a key role in enabling smart cities, asset tracking, smart utilities, agriculture and security infrastructures.

URLLC will make it possible for devices and machines to communicate with ultra-reliability, very low latency and high availability, making it ideal for vehicular communication, industrial control, factory automation, remote surgery, smart grids and public safety applications. URLLC aims ˜1 ms of latency. URLLC includes new services that will change the industry through links with ultra-reliability/low latency, such as remote control of key infrastructure and self-driving vehicles. The level of reliability and latency is essential for smart grid control, industrial automation, robotics, drones control and coordination.

Next, a plurality of use cases included in the triangle of FIG. 1 will be described in more detail.

5G can complement fiber-to-the-home (FTTH) and cable-based broadband (or DOCSIS) as a means of delivering streams rated from hundreds of megabits per second to gigabits per second. This high speed can be required to deliver TVs with resolutions of 4K or more (6K, 8K and above) as well as virtual reality (VR) and augmented reality (AR). VR and AR applications include mostly immersive sporting events. Certain applications may require special network settings. For example, in the case of a VR game, a game company may need to integrate a core server with an edge network server of a network operator to minimize delay.

Automotive is expected to become an important new driver for 5G, with many use cases for mobile communications to vehicles. For example, entertainment for passengers demands high capacity and high mobile broadband at the same time. This is because future users will continue to expect high-quality connections regardless of their location and speed. Another use case in the automotive sector is an augmented reality dashboard. The driver can identify an object in the dark on top of what is being viewed through the front window through the augmented reality dashboard. The augmented reality dashboard displays information that will inform the driver about the object's distance and movement. In the future, the wireless module enables communication between vehicles, information exchange between the vehicle and the supporting infrastructure, and information exchange between the vehicle and other connected devices (e.g. devices accompanied by a pedestrian). The safety system allows the driver to guide the alternative course of action so that he can drive more safely, thereby reducing the risk of accidents. The next step will be a remotely controlled vehicle or self-driving vehicle. This requires a very reliable and very fast communication between different self-driving vehicles and between vehicles and infrastructure. In the future, a self-driving vehicle will perform all driving activities, and the driver will focus only on traffic that the vehicle itself cannot identify. The technical requirements of self-driving vehicles require ultra-low latency and high-speed reliability to increase traffic safety to a level not achievable by humans.

Smart cities and smart homes, which are referred to as smart societies, will be embedded in high density wireless sensor networks. The distributed network of intelligent sensors will identify conditions for cost and energy-efficient maintenance of a city or house. A similar setting can be performed for each home. Temperature sensors, windows and heating controllers, burglar alarms and appliances are all wirelessly connected. Many of these sensors typically require low data rate, low power and low cost. However, for example, real-time high-definition (HD) video may be required for certain types of devices for monitoring.

The consumption and distribution of energy, including heat or gas, is highly dispersed, requiring automated control of distributed sensor networks. The smart grid interconnects these sensors using digital information and communication technologies to collect and act on information. This information can include supplier and consumer behavior, allowing the smart grid to improve the distribution of fuel, such as electricity, in terms of efficiency, reliability, economy, production sustainability, and automated methods. The smart grid can be viewed as another sensor network with low latency.

The health sector has many applications that can benefit from mobile communications. Communication systems can support telemedicine to provide clinical care in remote locations. This can help to reduce barriers to distance and improve access to health services that are not continuously available in distant rural areas. It is also used to save lives in critical care and emergency situations. Mobile communication based wireless sensor networks can provide remote monitoring and sensors for parameters such as heart rate and blood pressure.

Wireless and mobile communications are becoming increasingly important in industrial applications. Wiring costs are high for installation and maintenance. Thus, the possibility of replacing a cable with a wireless link that can be reconfigured is an attractive opportunity in many industries. However, achieving this requires that wireless connections operate with similar delay, reliability, and capacity as cables and that their management is simplified. Low latency and very low error probabilities are new requirements that need to be connected to 5G.

Logistics and freight tracking are important use cases of mobile communications that enable tracking of inventory and packages anywhere using location based information systems. Use cases of logistics and freight tracking typically require low data rates, but require a large range and reliable location information.

NR supports multiple numerology (or, subcarrier spacing (SCS)) to support various 5G services. For example, when the SCS is 15 kHz, wide area in traditional cellular bands may be supported. When the SCS is 30 kHz/60 kHz, dense-urban, lower latency and wider carrier bandwidth may be supported. When the SCS is 60 kHz or higher, a bandwidth greater than 24.25 GHz may be supported to overcome phase noise.

The NR frequency band may be defined as two types of frequency range, i.e., FR1 and FR2. The numerical value of the frequency range may be changed. For example, the frequency ranges of the two types (FR1 and FR2) may be as shown in Table 1 below. For ease of explanation, in the frequency ranges used in the NR system, FR1 may mean “sub 6 GHz range”, FR2 may mean “above 6 GHz range,” and may be referred to as millimeter wave (mmW).

TABLE 1 Frequency Range Corresponding designation frequency range Subcarrier Spacing FR1  450 MHz-6000 MHz  15, 30, 60 kHz FR2 24250 MHz-52600 MHz 60, 120, 240 kHz

As mentioned above, the numerical value of the frequency range of the NR system may be changed. For example, FR1 may include a frequency band of 410MHz to 7125MHz as shown in Table 2 below. That is, FR1 may include a frequency band of 6GHz (or 5850, 5900, 5925 MHz, etc.) or more. For example, a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or more included in FR1 may include an unlicensed band. Unlicensed bands may be used for a variety of purposes, for example for communication for vehicles (e.g., autonomous driving).

TABLE 2 Frequency Range Corresponding designation frequency range Subcarrier Spacing FR1  410 MHz-7125 MHz  15, 30, 60 kHz FR2 24250 MHz-52600 MHz 60, 120, 240 kHz

FIG. 2 shows an example of a wireless communication system to which the technical features of the present disclosure can be applied. Referring to FIG. 2, the wireless communication system may include a first device 210 and a second device 220.

The first device 210 includes a base station, a network node, a transmitting UE, a receiving UE, a wireless device, a wireless communication device, a vehicle, a vehicle equipped with an autonomous driving function, a connected car, a drone, an unmanned aerial vehicle (UAV), an artificial intelligence (AI) module, a robot, an AR device, a VR device, a mixed reality (MR) device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a fin-tech device (or, a financial device), a security device, a climate/environmental device, a device related to 5G services, or a device related to the fourth industrial revolution.

The second device 220 includes a base station, a network node, a transmitting UE, a receiving UE, a wireless device, a wireless communication device, a vehicle, a vehicle equipped with an autonomous driving function, a connected car, a drone, a UAV, an AI module, a robot, an AR device, a VR device, an MR device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a fin-tech device (or, a financial device), a security device, a climate/environmental device, a device related to 5G services, or a device related to the fourth industrial revolution.

For example, the UE may include a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation device, a slate personal computer (PC), a tablet PC, an ultrabook, a wearable device (e.g. a smartwatch, a smart glass, a head mounted display (HMD)). For example, the HMD may be a display device worn on the head. For example, the HMD may be used to implement AR, VR and/or MR.

For example, the drone may be a flying object that is flying by a radio control signal without a person boarding it. For example, the VR device may include a device that implements an object or background in the virtual world. For example, the AR device may include a device that implements connection of an object and/or a background of a virtual world to an object and/or a background of the real world. For example, the MR device may include a device that implements fusion of an object and/or a background of a virtual world to an object and/or a background of the real world. For example, the hologram device may include a device that implements a 360-degree stereoscopic image by recording and playing stereoscopic information by utilizing a phenomenon of interference of light generated by the two laser lights meeting with each other, called holography. For example, the public safety device may include a video relay device or a video device that can be worn by the user's body. For example, the MTC device and the IoT device may be a device that do not require direct human intervention or manipulation. For example, the MTC device and the IoT device may include a smart meter, a vending machine, a thermometer, a smart bulb, a door lock and/or various sensors. For example, the medical device may be a device used for the purpose of diagnosing, treating, alleviating, handling, or preventing a disease. For example, the medical device may be a device used for the purpose of diagnosing, treating, alleviating, or correcting an injury or disorder. For example, the medical device may be a device used for the purpose of inspecting, replacing or modifying a structure or function. For example, the medical device may be a device used for the purpose of controlling pregnancy. For example, the medical device may include a treatment device, a surgical device, an (in vitro) diagnostic device, a hearing aid and/or a procedural device, etc. For example, a security device may be a device installed to prevent the risk that may occur and to maintain safety. For example, the security device may include a camera, a closed-circuit TV (CCTV), a recorder, or a black box. For example, the fin-tech device may be a device capable of providing financial services such as mobile payment. For example, the fin-tech device may include a payment device or a point of sales (POS). For example, the climate/environmental device may include a device for monitoring or predicting the climate/environment.

The first device 210 may include at least one or more processors, such as a processor 211, at least one memory, such as a memory 212, and at least one transceiver, such as a transceiver 213. The processor 211 may perform the functions, procedures, and/or methods of the first device described throughout the disclosure. The processor 211 may perform one or more protocols. For example, the processor 211 may perform one or more layers of the air interface protocol. The memory 212 is connected to the processor 211 and may store various types of information and/or instructions. The transceiver 213 is connected to the processor 211 and may be controlled by the processor 211 to transmit and receive wireless signals.

The second device 220 may include at least one or more processors, such as a processor 221, at least one memory, such as a memory 222, and at least one transceiver, such as a transceiver 223. The processor 221 may perform the functions, procedures, and/or methods of the second device 220 described throughout the disclosure. The processor 221 may perform one or more protocols. For example, the processor 221 may perform one or more layers of the air interface protocol. The memory 222 is connected to the processor 221 and may store various types of information and/or instructions. The transceiver 223 is connected to the processor 221 and may be controlled by the processor 221 to transmit and receive wireless signals.

The memory 212, 222 may be connected internally or externally to the processor 211, 212, or may be connected to other processors via a variety of technologies such as wired or wireless connections.

The first device 210 and/or the second device 220 may have more than one antenna. For example, antenna 214 and/or antenna 224 may be configured to transmit and receive wireless signals.

FIG. 3 shows an example of a wireless communication system to which the technical features of the present disclosure can be applied.

Specifically, FIG. 3 shows a system architecture based on an evolved-UMTS terrestrial radio access network (E-UTRAN). The aforementioned LTE is a part of an evolved-UTMS (e-UMTS) using the E-UTRAN.

Referring to FIG. 3, the wireless communication system includes one or more user equipment (UE) 310, an E-UTRAN and an evolved packet core (EPC). The UE 310 refers to a communication equipment carried by a user. The UE 310 may be fixed or mobile. The UE 310 may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, etc.

The E-UTRAN consists of one or more evolved NodeB (eNB) 320. The eNB 320 provides the E-UTRA user plane and control plane protocol terminations towards the UE 10. The eNB 320 is generally a fixed station that communicates with the UE 310. The eNB 320 hosts the functions, such as inter-cell radio resource management (RRM), radio bearer (RB) control, connection mobility control, radio admission control, measurement configuration/provision, dynamic resource allocation (scheduler), etc. The eNB 320 may be referred to as another terminology, such as a base station (BS), a base transceiver system (BTS), an access point (AP), etc.

A downlink (DL) denotes communication from the eNB 320 to the UE 310. An uplink (UL) denotes communication from the UE 310 to the eNB 320. A sidelink (SL) denotes communication between the UEs 310. In the DL, a transmitter may be a part of the eNB 320, and a receiver may be a part of the UE 310. In the UL, the transmitter may be a part of the UE 310, and the receiver may be a part of the eNB 320. In the SL, the transmitter and receiver may be a part of the UE 310.

The EPC includes a mobility management entity (MME), a serving gateway (S-GW) and a packet data network (PDN) gateway (P-GW). The MME hosts the functions, such as non-access stratum (NAS) security, idle state mobility handling, evolved packet system (EPS) bearer control, etc. The S-GW hosts the functions, such as mobility anchoring, etc. The S-GW is a gateway having an E-UTRAN as an endpoint. For convenience, MME/S-GW 330 will be referred to herein simply as a “gateway,” but it is understood that this entity includes both the MME and S-GW. The P-GW hosts the functions, such as UE Internet protocol (IP) address allocation, packet filtering, etc. The P-GW is a gateway having a PDN as an endpoint. The P-GW is connected to an external network.

The UE 310 is connected to the eNB 320 by means of the Uu interface. The UEs 310 are interconnected with each other by means of the PC5 interface. The eNBs 320 are interconnected with each other by means of the X2 interface. The eNBs 320 are also connected by means of the S1 interface to the EPC, more specifically to the MME by means of the S1-MME interface and to the S-GW by means of the S1-U interface. The S1 interface supports a many-to-many relation between MMEs/S-GWs and eNBs.

FIG. 4 shows another example of a wireless communication system to which the technical features of the present disclosure can be applied.

Specifically, FIG. 4 shows a system architecture based on a 5G NR. The entity used in the 5G NR (hereinafter, simply referred to as “NR”) may absorb some or all of the functions of the entities introduced in FIG. 3 (e.g. eNB, MME, S-GW). The entity used in the NR may be identified by the name “NG” for distinction from the LTE/LTE-A.

Referring to FIG. 4, the wireless communication system includes one or more UE 410, a next-generation RAN (NG-RAN) and a 5th generation core network (5GC). The NG-RAN consists of at least one NG-RAN node. The NG-RAN node is an entity corresponding to the eNB 320 shown in FIG. 3. The NG-RAN node consists of at least one gNB 421 and/or at least one ng-eNB 422. The gNB 421 provides NR user plane and control plane protocol terminations towards the UE 410. The ng-eNB 422 provides E-UTRA user plane and control plane protocol terminations towards the UE 410.

The 5GC includes an access and mobility management function (AMF), a user plane function (UPF) and a session management function (SMF). The AMF hosts the functions, such as NAS security, idle state mobility handling, etc. The AMF is an entity including the functions of the conventional MME. The UPF hosts the functions, such as mobility anchoring, protocol data unit (PDU) handling. The UPF an entity including the functions of the conventional S-GW. The SMF hosts the functions, such as UE IP address allocation, PDU session control.

The gNBs 421 and ng-eNBs 422 are interconnected with each other by means of the Xn interface. The gNBs 421 and ng-eNBs 422 are also connected by means of the NG interfaces to the 5GC, more specifically to the AMF by means of the NG-C interface and to the UPF by means of the NG-U interface.

A protocol structure between network entities described above is described. On the system of FIG. 3 and/or FIG. 4, layers of a radio interface protocol between the UE and the network (e.g. NG-RAN and/or E-UTRAN) may be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the open system interconnection (OSI) model that is well-known in the communication system.

FIG. 5 shows a block diagram of a user plane protocol stack to which the technical features of the present disclosure can be applied. FIG. 6 shows a block diagram of a control plane protocol stack to which the technical features of the present disclosure can be applied.

The user/control plane protocol stacks shown in FIG. 5 and FIG. 6 are used in NR. However, user/control plane protocol stacks shown in FIG. 5 and FIG. 6 may be used in LTE/LTE-A without loss of generality, by replacing gNB/AMF with eNB/MME.

Referring to FIG. 5 and FIG. 6, a physical (PHY) layer belonging to L1. The PHY layer offers information transfer services to media access control (MAC) sublayer and higher layers. The PHY layer offers to the MAC sublayer transport channels. Data between the MAC sublayer and the PHY layer is transferred via the transport channels. Between different PHY layers, i.e., between a PHY layer of a transmission side and a PHY layer of a reception side, data is transferred via the physical channels.

The MAC sublayer belongs to L2. The main services and functions of the MAC sublayer include mapping between logical channels and transport channels, multiplexing/de-multiplexing of MAC service data units (SDUs) belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels, scheduling information reporting, error correction through hybrid automatic repeat request (HARD), priority handling between UEs by means of dynamic scheduling, priority handling between logical channels of one UE by means of logical channel prioritization (LCP), etc. The MAC sublayer offers to the radio link control (RLC) sublayer logical channels.

The RLC sublayer belong to L2. The RLC sublayer supports three transmission modes, i.e. transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM), in order to guarantee various quality of services (QoS) required by radio bearers. The main services and functions of the RLC sublayer depend on the transmission mode. For example, the RLC sublayer provides transfer of upper layer PDUs for all three modes, but provides error correction through ARQ for AM only. In LTE/LTE-A, the RLC sublayer provides concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer) and re-segmentation of RLC data PDUs (only for AM data transfer). In NR, the RLC sublayer provides segmentation (only for AM and UM) and re-segmentation (only for AM) of RLC SDUs and reassembly of SDU (only for AM and UM). That is, the NR does not support concatenation of RLC SDUs. The RLC sublayer offers to the packet data convergence protocol (PDCP) sublayer RLC channels.

The PDCP sublayer belong to L2. The main services and functions of the PDCP sublayer for the user plane include header compression and decompression, transfer of user data, duplicate detection, PDCP PDU routing, retransmission of PDCP SDUs, ciphering and deciphering, etc. The main services and functions of the PDCP sublayer for the control plane include ciphering and integrity protection, transfer of control plane data, etc.

The service data adaptation protocol (SDAP) sublayer belong to L2. The SDAP sublayer is only defined in the user plane. The SDAP sublayer is only defined for NR. The main services and functions of SDAP include, mapping between a QoS flow and a data radio bearer (DRB), and marking QoS flow ID (QFI) in both DL and UL packets. The SDAP sublayer offers to 5GC QoS flows.

A radio resource control (RRC) layer belongs to L3. The RRC layer is only defined in the control plane. The RRC layer controls radio resources between the UE and the network. To this end, the RRC layer exchanges RRC messages between the UE and the BS. The main services and functions of the RRC layer include broadcast of system information related to AS and NAS, paging, establishment, maintenance and release of an RRC connection between the UE and the network, security functions including key management, establishment, configuration, maintenance and release of radio bearers, mobility functions, QoS management functions, UE measurement reporting and control of the reporting, NAS message transfer to/from NAS from/to UE.

In other words, the RRC layer controls logical channels, transport channels, and physical channels in relation to the configuration, reconfiguration, and release of radio bearers. A radio bearer refers to a logical path provided by L1 (PHY layer) and L2 (MAC/RLC/PDCP/SDAP sublayer) for data transmission between a UE and a network. Setting the radio bearer means defining the characteristics of the radio protocol layer and the channel for providing a specific service, and setting each specific parameter and operation method. Radio bearer may be divided into signaling RB (SRB) and data RB (DRB). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

An RRC state indicates whether an RRC layer of the UE is logically connected to an RRC layer of the E-UTRAN. In LTE/LTE-A, when the RRC connection is established between the RRC layer of the UE and the RRC layer of the E-UTRAN, the UE is in the RRC connected state (RRC_CONNECTED). Otherwise, the UE is in the RRC idle state (RRC_IDLE). In NR, the RRC inactive state (RRC_INACTIVE) is additionally introduced. RRC_INACTIVE may be used for various purposes. For example, the massive machine type communications (MMTC) UEs can be efficiently managed in RRC_INACTIVE. When a specific condition is satisfied, transition is made from one of the above three states to the other.

A predetermined operation may be performed according to the RRC state. In RRC_IDLE, public land mobile network (PLMN) selection, broadcast of system information (SI), cell re-selection mobility, core network (CN) paging and discontinuous reception (DRX) configured by NAS may be performed. The UE shall have been allocated an identifier (ID) which uniquely identifies the UE in a tracking area. No RRC context stored in the BS.

In RRC_CONNECTED, the UE has an RRC connection with the network (i.e. E-UTRAN/NG-RAN). Network-CN connection (both C/U-planes) is also established for UE. The UE AS context is stored in the network and the UE. The RAN knows the cell which the UE belongs to. The network can transmit and/or receive data to/from UE. Network controlled mobility including measurement is also performed.

Most of operations performed in RRC_IDLE may be performed in RRC_INACTIVE. But, instead of CN paging in RRC_IDLE, RAN paging is performed in RRC_INACTIVE. In other words, in RRC_IDLE, paging for mobile terminated (MT) data is initiated by core network and paging area is managed by core network. In RRC_INACTIVE, paging is initiated by NG-RAN, and RAN-based notification area (RNA) is managed by NG-RAN. Further, instead of DRX for CN paging configured by NAS in RRC_IDLE, DRX for RAN paging is configured by NG-RAN in RRC_INACTIVE. Meanwhile, in RRC_INACTIVE, 5GC-NG-RAN connection (both C/U-planes) is established for UE, and the UE AS context is stored in NG-RAN and the UE. NG-RAN knows the RNA which the UE belongs to.

NAS layer is located at the top of the RRC layer. The NAS control protocol performs the functions, such as authentication, mobility management, security control.

The physical channels may be modulated according to OFDM processing and utilizes time and frequency as radio resources. The physical channels consist of a plurality of orthogonal frequency division multiplexing (OFDM) symbols in time domain and a plurality of subcarriers in frequency domain. One subframe consists of a plurality of OFDM symbols in the time domain. A resource block is a resource allocation unit, and consists of a plurality of OFDM symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific OFDM symbols (e.g. first OFDM symbol) of the corresponding subframe for a physical downlink control channel (PDCCH), i.e. L1/L2 control channel. A transmission time interval (TTI) is a basic unit of time used by a scheduler for resource allocation. The TTI may be defined in units of one or a plurality of slots, or may be defined in units of mini-slots.

The transport channels are classified according to how and with what characteristics data are transferred over the radio interface. DL transport channels include a broadcast channel (BCH) used for transmitting system information, a downlink shared channel (DL-SCH) used for transmitting user traffic or control signals, and a paging channel (PCH) used for paging a UE. UL transport channels include an uplink shared channel (UL-SCH) for transmitting user traffic or control signals and a random access channel (RACH) normally used for initial access to a cell.

Different kinds of data transfer services are offered by MAC sublayer. Each logical channel type is defined by what type of information is transferred. Logical channels are classified into two groups: control channels and traffic channels.

Control channels are used for the transfer of control plane information only. The control channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH) and a dedicated control channel (DCCH). The BCCH is a DL channel for broadcasting system control information. The PCCH is DL channel that transfers paging information, system information change notifications. The CCCH is a channel for transmitting control information between UEs and network. This channel is used for UEs having no RRC connection with the network. The DCCH is a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. This channel is used by UEs having an RRC connection.

Traffic channels are used for the transfer of user plane information only. The traffic channels include a dedicated traffic channel (DTCH). The DTCH is a point-to-point channel, dedicated to one UE, for the transfer of user information. The DTCH can exist in both UL and DL.

Regarding mapping between the logical channels and transport channels, in DL, BCCH can be mapped to BCH, BCCH can be mapped to DL-SCH, PCCH can be mapped to PCH, CCCH can be mapped to DL-SCH, DCCH can be mapped to DL-SCH, and DTCH can be mapped to DL-SCH. In UL, CCCH can be mapped to UL-SCH, DCCH can be mapped to UL-SCH, and DTCH can be mapped to UL-SCH.

FIG. 7 illustrates a frame structure in a 3GPP based wireless communication system.

The frame structure illustrated in FIG. 7 is purely exemplary and the number of subframes, the number of slots, and/or the number of symbols in a frame may be variously changed. In the 3GPP based wireless communication system, an OFDM numerology (e.g., subcarrier spacing (SCS), transmission time interval (TTI) duration) may be differently configured between a plurality of cells aggregated for one UE. For example, if a UE is configured with different SCSs for cells aggregated for the cell, an (absolute time) duration of a time resource (e.g. a subframe, a slot, or a TTI) including the same number of symbols may be different among the aggregated cells. Herein, symbols may include OFDM symbols (or CP-OFDM symbols), SC-FDMA symbols (or discrete Fourier transform-spread-OFDM (DFT-s-OFDM) symbols).

Referring to FIG. 7, downlink and uplink transmissions are organized into frames. Each frame has Tf=10 ms duration. Each frame is divided into two half-frames, where each of the half-frames has 5 ms duration. Each half-frame consists of 5 subframes, where the duration Tsf per subframe is 1 ms. Each subframe is divided into slots and the number of slots in a subframe depends on a subcarrier spacing. Each slot includes 14 or 12 OFDM symbols based on a cyclic prefix (CP). In a normal CP, each slot includes 14 OFDM symbols and, in an extended CP, each slot includes 12 OFDM symbols. The numerology is based on exponentially scalable subcarrier spacing Δf=2u*15 kHz. The following table shows the number of OFDM symbols per slot, the number of slots per frame, and the number of slots per for the normal CP, according to the subcarrier spacing Δf=2u*15 kHz.

TABLE 3 u Nslotsymb Nframe, uslot Nsubframe, uslot 0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16

The following table shows the number of OFDM symbols per slot, the number of slots per frame, and the number of slots per for the extended CP, according to the subcarrier spacing Δf=2u*15 kHz.

TABLE 4 u Nslotsymb Nframe, uslot Nsubframe, uslot 2 12 40 4

A slot includes plural symbols (e.g., 14 or 12 symbols) in the time domain. For each numerology (e.g. subcarrier spacing) and carrier, a resource grid of Nsize,ugrid,x*NRBsc subcarriers and Nsubframe,usymb OFDM symbols is defined, starting at common resource block (CRB) Nstart,ugrid indicated by higher-layer signaling (e.g. radio resource control (RRC) signaling), where Nsize,ugrid,x is the number of resource blocks (RBs) in the resource grid and the subscript x is DL for downlink and UL for uplink. NRBsc is the number of subcarriers per RB. In the 3GPP based wireless communication system, NRBsc is 12 generally. There is one resource grid for a given antenna port p, subcarrier spacing configuration u, and transmission direction (DL or UL). The carrier bandwidth Nsize,ugrid for subcarrier spacing configuration u is given by the higher-layer parameter (e.g. RRC parameter). Each element in the resource grid for the antenna port p and the subcarrier spacing configuration u is referred to as a resource element (RE) and one complex symbol may be mapped to each RE. Each RE in the resource grid is uniquely identified by an index k in the frequency domain and an index 1 representing a symbol location relative to a reference point in the time domain. In the 3GPP based wireless communication system, an RB is defined by 12 consecutive subcarriers in the frequency domain. In the 3GPP NR system, RBs are classified into CRBs and physical resource blocks (PRBs). CRBs are numbered from 0 and upwards in the frequency domain for subcarrier spacing configuration u. The center of subcarrier 0 of CRB 0 for subcarrier spacing configuration u coincides with ‘point A’ which serves as a common reference point for resource block grids. In the 3GPP NR system, PRBs are defined within a bandwidth part (BWP) and numbered from 0 to NsizeBWP,i−1, where i is the number of the bandwidth part. The relation between the physical resource block nPRB in the bandwidth part i and the common resource block nCRB is as follows: nPRB=nCRB+NsizeBWP,i, where NsizeBWP,i is the common resource block where bandwidth part starts relative to CRB 0. The BWP includes a plurality of consecutive RBs. A carrier may include a maximum of N (e.g., 5) BWPs. A UE may be configured with one or more BWPs on a given component carrier. Only one BWP among BWPs configured to the UE can active at a time. The active BWP defines the UE's operating bandwidth within the cell's operating bandwidth.

In the present disclosure, the term “cell” may refer to a geographic area to which one or more nodes provide a communication system, or refer to radio resources. A “cell” of a geographic area may be understood as coverage within which a node can provide service using a carrier and a “cell” as radio resources (e.g. time-frequency resources) is associated with bandwidth (BW) which is a frequency range configured by the carrier. The “cell” associated with the radio resources is defined by a combination of downlink resources and uplink resources, for example, a combination of a downlink (DL) component carrier (CC) and a uplink (UL) CC. The cell may be configured by downlink resources only, or may be configured by downlink resources and uplink resources. Since DL coverage, which is a range within which the node is capable of transmitting a valid signal, and UL coverage, which is a range within which the node is capable of receiving the valid signal from the UE, depends upon a carrier carrying the signal, the coverage of the node may be associated with coverage of the “cell” of radio resources used by the node. Accordingly, the term “cell” may be used to represent service coverage of the node sometimes, radio resources at other times, or a range that signals using the radio resources can reach with valid strength at other times.

In carrier aggregation (CA), two or more CCs are aggregated. A UE may simultaneously receive or transmit on one or multiple CCs depending on its capabilities. CA is supported for both contiguous and non-contiguous CCs. When CA is configured the UE only has one radio resource control (RRC) connection with the network. At RRC connection establishment/re-establishment/handover, one serving cell provides the non-access stratum (NAS) mobility information, and at RRC connection re-establishment/handover, one serving cell provides the security input. This cell is referred to as the Primary Cell (PCell). The PCell is a cell, operating on the primary frequency, in which the UE either performs the initial connection establishment procedure or initiates the connection re-establishment procedure. Depending on UE capabilities, Secondary Cells (SCells) can be configured to form together with the PCell a set of serving cells. An SCell is a cell providing additional radio resources on top of Special Cell. The configured set of serving cells for a UE therefore always consists of one PCell and one or more SCells. For dual connectivity operation, the term Special Cell (SpCell) refers to the PCell of the master cell group (MCG) or the PSCell of the secondary cell group (SCG). An SpCell supports PUCCH transmission and contention-based random access, and is always activated. The MCG is a group of serving cells associated with a master node, comprising of the SpCell (PCell) and optionally one or more SCells. The SCG is the subset of serving cells associated with a secondary node, comprising of the PSCell and zero or more SCells, for a UE configured with dual connectivity (DC). For a UE in RRC_CONNECTED not configured with CA/DC there is only one serving cell comprising of the PCell. For a UE in RRC_CONNECTED configured with CA/DC the term “serving cells” is used to denote the set of cells comprising of the SpCell(s) and all SCells. In DC, two MAC entities are configured in a UE: one for the MCG and one for the SCG.

FIG. 8 illustrates a data flow example in the 3GPP NR system.

In FIG. 8, “RB” denotes a radio bearer, and “H” denotes a header. Radio bearers are categorized into two groups: data radio bearers (DRB) for user plane data and signalling radio bearers (SRB) for control plane data. The MAC PDU is transmitted/received using radio resources through the PHY layer to/from an external device. The MAC PDU arrives to the PHY layer in the form of a transport block.

In the PHY layer, the uplink transport channels UL-SCH and RACH are mapped to their physical channels PUSCH and PRACH, respectively, and the downlink transport channels DL-SCH, BCH and PCH are mapped to PDSCH, PBCH and PDSCH, respectively. In the PHY layer, uplink control information (UCI) is mapped to PUCCH, and downlink control information (DCI) is mapped to PDCCH. A MAC PDU related to UL-SCH is transmitted by a UE via a PUSCH based on an UL grant, and a MAC PDU related to DL-SCH is transmitted by a BS via a PDSCH based on a DL assignment.

Data unit(s) (e.g. PDCP SDU, PDCP PDU, RLC SDU, RLC PDU, RLC SDU, MAC SDU, MAC CE, MAC PDU) in the present disclosure is(are) transmitted/received on a physical channel (e.g. PDSCH, PUSCH) based on resource allocation (e.g. UL grant, DL assignment). In the present disclosure, uplink resource allocation is also referred to as uplink grant, and downlink resource allocation is also referred to as downlink assignment. The resource allocation includes time domain resource allocation and frequency domain resource allocation. In the present disclosure, an uplink grant is either received by the UE dynamically on PDCCH, in a Random Access Response, or configured to the UE semi-persistently by RRC. In the present disclosure, downlink assignment is either received by the UE dynamically on the PDCCH, or configured to the UE semi-persistently by RRC signalling from the BS.

FIG. 9 shows an example of a dual connectivity (DC) architecture to which technical features of the present disclosure can be applied. In FIG. 9 and throughout the disclosure, ‘radio access network (RAN) node’ refers to a network entity to which a wireless device can access through a radio channel. Examples of the RAN node may comprise gNB, eNB, base station, and/or cell.

Referring to FIG. 9, MN 911, SN 921, and a UE 930 communicating with both the MN 911 and the SN 921 are illustrated. As illustrated in FIG. 9, DC refers to a scheme in which a UE (e.g., UE 930) utilizes radio resources provided by at least two RAN nodes comprising a MN (e.g., MN 911) and one or more SNs (e.g., SN 921). In other words, DC refers to a scheme in which a UE is connected to both the MN and the one or more SNs, and communicates with both the MN and the one or more SNs. Since the MN and the SN may be in different sites, a backhaul between the MN and the SN may be construed as non-ideal backhaul (e.g., relatively large delay between nodes).

MN (e.g., MN 911) refers to a main RAN node providing services to a UE in DC situation. SN (e.g., SN 921) refers to an additional RAN node providing services to the UE with the MN in the DC situation. If one RAN node provides services to a UE, the RAN node may be a MN. SN can exist if MN exists.

For example, the MN may be associated with macro cell whose coverage is relatively larger than that of a small cell. However, the MN does not have to be associated with macro cell—that is, the MN may be associated with a small cell. Throughout the disclosure, a RAN node that is associated with a macro cell may be referred to as ‘macro cell node’. MN may comprise macro cell node.

For example, the SN may be associated with small cell (e.g., micro cell, pico cell, femto cell) whose coverage is relatively smaller than that of a macro cell. However, the SN does not have to be associated with small cell—that is, the SN may be associated with a macro cell. Throughout the disclosure, a RAN node that is associated with a small cell may be referred to as ‘small cell node’. SN may comprise small cell node.

The MN may be associated with a master cell group (MCG). MCG may refer to a group of serving cells associated with the MN, and may comprise a primary cell (PCell) and optionally one or more secondary cells (SCells). User plane data and/or control plane data may be transported from a core network to the MN through a MCG bearer. MCG bearer refers to a bearer whose radio protocols are located in the MN to use MN resources. As shown in FIG. 9, the radio protocols of the MCG bearer may comprise PDCP, RLC, MAC and/or PHY.

The SN may be associated with a secondary cell group (SCG). SCG may refer to a group of serving cells associated with the SN, and may comprise a primary secondary cell (PSCell) and optionally one or more SCells. User plane data may be transported from a core network to the SN through a SCG bearer. SCG bearer refers to a bearer whose radio protocols are located in the SN to use SN resources. As shown in FIG. 9, the radio protocols of the SCG bearer may comprise PDCP, RLC, MAC and PHY.

User plane data and/or control plane data may be transported from a core network to the MN and split up/duplicated in the MN, and at least part of the split/duplicated data may be forwarded to the SN through a split bearer. Split bearer refers to a bearer whose radio protocols are located in both the MN and the SN to use both MN resources and SN resources. As shown in FIG. 9, the radio protocols of the split bearer located in the MN may comprise PDCP, RLC, MAC and PHY. The radio protocols of the split bearer located in the SN may comprise RLC, MAC and PHY.

According to various embodiments, PDCP anchor/PDCP anchor point/PDCP anchor node refers to a RAN node comprising a PDCP entity which splits up and/or duplicates data and forwards at least part of the split/duplicated data over X2/Xn interface to another RAN node. In the example of FIG. 9, PDCP anchor node may be MN.

According to various embodiments, the MN for the UE may be changed. This may be referred to as handover, or a MN handover.

According to various embodiments, a SN may newly start providing radio resources to the UE, establishing a connection with the UE, and/or communicating with the UE (i.e., SN for the UE may be newly added). This may be referred to as a SN addition.

According to various embodiments, a SN for the UE may be changed while the MN for the UE is maintained. This may be referred to as a SN change.

According to various embodiments, DC may comprise E-UTRAN NR-DC (EN-DC), and/or multi-radio access technology (RAT)-DC (MR-DC). EN-DC refers to a DC situation in which a UE utilizes radio resources provided by E-UTRAN node and NR RAN node. MR-DC refers to a DC situation in which a UE utilizes radio resources provided by RAN nodes with different RATs.

FIG. 10 shows an example of handover procedure to which technical features of the present disclosure can be applied. FIG. 10 illustrates steps for the handover procedure exemplary, but the illustrated steps can also be applied to a mobility procedure (e.g., SN addition procedure and/or SN change procedure).

Referring to FIG. 10, in step S1001, the source RAN node may transmit measurement control message to the UE. The source RAN node may configure the UE measurement procedures according to the roaming and access restriction information and, for example, the available multiple frequency band information through the measurement control message. Measurement control information provided by the source RAN node through the measurement control message may assist the function controlling the UE's connection mobility. For example, the measurement control message may comprise measurement configuration and/or report configuration.

In step S1003, the UE may transmit a measurement report message to the source RAN node. The measurement report message may comprise a result of measurement on neighbor cell(s) around the UE which can be detected by the UE. The UE may generate the measurement report message according to a measurement configuration and/or measurement control information in the measurement control message received in step S1001.

In step S1005, the source RAN node may make a handover (HO) decision based on the measurement report. For example, the source RAN node may make a HO decision and determine a target RAN node for HO among neighbor cells around the UE based on a result of measurement (e.g., cell quality, signal quality, signal strength, reference signal received power (RSRP), reference signal received quality (RSRP), channel state, channel quality, signal to interference plus noise ratio (SINR)) on the neighbor cells.

In step S1007, the source RAN node may transmit a HO request message to the target RAN node which is determined in step S1005. That is, the source RAN node may perform handover preparation with the target RAN node. The HO request message may comprise necessary information to prepare the handover at the target RAN node.

In step S1009, the target RAN node may perform an admission control based on information included in the HO request message. The target RAN node may configure and reserve the required resources (e.g., C-RNTI and/or RACH preamble). The AS-configuration to be used in the target RAN node can either be specified independently (i.e. an “establishment”) or as a delta compared to the AS-configuration used in the source RAN node (i.e. a “reconfiguration”).

In step S1011, the target RAN node may transmit a HO request acknowledge (ACK) message to the source RAN node. The HO request ACK message may comprise information on resources reserved and prepared for a handover. For example, the HO request ACK message may comprise a transparent container to be sent to the UE as an RRC message to perform the handover. The container may include a new C-RNTI, target gNB security algorithm identifiers for the selected security algorithms, a dedicated RACH preamble, and/or possibly some other parameters i.e. access parameters, SIBs. If RACH-less handover is configured, the container may include timing adjustment indication and optionally a preallocated uplink grant. The HO request ACK message may also include RNL/TNL information for forwarding tunnels, if necessary. As soon as the source RAN node receives the HO request ACK message, or as soon as the transmission of the handover command is initiated in the downlink, data forwarding may be initiated.

In step S1013, the source RAN node may transmit a handover command which may be a RRC message, to the UE. The target RAN node may generate the RRC message to perform the handover, i.e. RRCConnectionReconfiguration message including the mobilityControllnformation, to be sent by the source RAN node towards the UE. The source RAN node may perform the necessary integrity protection and ciphering of the message. The UE may receive the RRCConnectionReconfiguration message with necessary parameters (i.e. new C-RNTI, target eNB security algorithm identifiers, and optionally dedicated RACH preamble, target eNB SIBs, etc.) and is commanded by the source eNB to perform the handover. If RACH-less handover is configured, the RRCConnectionReconfiguration may include timing adjustment indication and optionally preallocated uplink grant for accessing the target RAN node. If preallocated uplink grant is not included, the UE should monitor PDCCH of the target RAN node to receive an uplink grant. The UE may not need to delay the handover execution for delivering the HARQ/ARQ responses to source RAN node. If Make-Before-Break HO is configured, the connection to the source RAN node may be maintained after the reception of RRCConnectionReconfiguration message with mobilityControllnformation before the UE executes initial uplink transmission to the target RAN node.

In step S1015, the UE may switch to a new cell i.e., the target RAN node. The UE may detach from the old cell i.e., the source RAN node and synchronize to a new cell i.e., the target RAN node. For example, the UE may perform a random access to the target RAN node. The UE may transmit a random access preamble to the target RAN node, and receive a random access response comprising an uplink grant from the target RAN node. If RACH-less handover is configured, the step S1015 may be omitted, and the uplink grant may be provided in step S1013. The uplink grant may be used for the UE to transmit a handover complete message to the target RAN node.

In step S1017, the UE may transmit a handover complete message (i.e., RRCConnectionReconfigurationComplete message) to the target RAN node. When the UE has successfully accessed the target RAN node or received uplink grant when RACH-less HO is configured, the UE may send the RRCConnectionReconfigurationComplete message comprising a C-RNTI to confirm the handover, along with an uplink Buffer Status Report, whenever possible, to the target RAN node to indicate that the handover procedure is completed for the UE. The target RAN node may verify the C-RNTI sent in the RRCConnectionReconfigurationComplete message. The target RAN node can now begin sending data to the UE.

FIG. 11 shows an example of a conditional handover procedure to which technical features of the present disclosure can be applied. FIG. 11 illustrates steps for the conditional handover procedure exemplary, but the illustrated steps can also be applied to a conditional mobility procedure (e.g., conditional SN addition procedure and/or conditional SN change procedure).

Referring to FIG. 11, in step S1101, the source RAN node may transmit measurement control message to the UE. The source RAN node may configure the UE measurement procedures according to the roaming and access restriction information and, for example, the available multiple frequency band information through the measurement control message. Measurement control information provided by the source RAN node through the measurement control message may assist the function controlling the UE's connection mobility. For example, the measurement control message may comprise measurement configuration and/or report configuration.

In step S1103, the UE may transmit a measurement report message to the source RAN node. The measurement report message may comprise a result of measurement on neighbor cell(s) around the UE which can be detected by the UE. The UE may generate the measurement report message according to a measurement configuration and/or measurement control information in the measurement control message received in step S1101.

In step S1105, the source RAN node may make a handover (HO) decision based on the measurement report. For example, the source RAN node may make a HO decision and determine candidate target RAN nodes (e.g., cell quality, signal quality, signal strength, reference signal received power (RSRP), reference signal received quality (RSRP), channel state, channel quality, signal to interference plus noise ratio (SINR)) on the neighbor cells.

In step S1107, the source RAN node may transmit HO request messages to the target RAN node 1 and the target RAN node 2 which are determined in step S1105. That is, the source RAN node may perform handover preparation with the target RAN node 1 and the target RAN node 2. The HO request message may comprise necessary information to prepare the handover at the target side (e.g., target RAN node 1 and target RAN node 2).

In step S1109, each of the target RAN node 1 and the target RAN node 2 may perform an admission control based on information included in the HO request message. The target RAN node may configure and reserve the required resources (e.g., C-RNTI and/or RACH preamble). The AS-configuration to be used in the target RAN node can either be specified independently (i.e. an “establishment”) or as a delta compared to the AS-configuration used in the source RAN node (i.e. a “reconfiguration”).

In step S1111, the target RAN node 1 and the target RAN node 2 may transmit a HO request acknowledge (ACK) message to the source RAN node. The HO request ACK message may comprise information on resources reserved and prepared for a handover. For example, the HO request ACK message may comprise a transparent container to be sent to the UE as an RRC message to perform the handover. The container may include a new C-RNTI, target gNB security algorithm identifiers for the selected security algorithms, a dedicated RACH preamble, and/or possibly some other parameters i.e. access parameters, SIBs. If RACH-less handover is configured, the container may include timing adjustment indication and optionally a preallocated uplink grant. The HO request ACK message may also include RNL/TNL information for forwarding tunnels, if necessary. As soon as the source RAN node receives the HO request ACK message, or as soon as the transmission of the handover command is initiated in the downlink, data forwarding may be initiated.

In step S1113, the source RAN node may transmit a conditional HO (CHO) configuration to the UE. The CHO configuration may be also referred to as conditional reconfiguration. The CHO configuration may comprise a CHO configuration for each of the candidate target RAN nodes (e.g., target RAN node 1, target RAN node 2). For example, the CHO configuration may comprise a CHO configuration for the target RAN node 1, and a CHO configuration for the target RAN node 2. The CHO configuration for the target RAN node 1 may comprise a handover condition for the target RAN node 1, and a handover command of the target RAN node 1. The handover command of the target RAN node 1 may comprise RRC reconfiguration parameters for a handover to the target RAN node 1, including information on resources reserved for the handover to the target RAN node 1. Similarly, the CHO configuration for the target RAN node 2 may comprise a handover condition for the target RAN node 2, and a handover command of the target RAN node 2. The handover command of the target RAN node 2 may comprise RRC reconfiguration parameters for a handover to the target RAN node 2, including information on resources reserved for the handover to the target RAN node 2.

In step S1115, the UE may perform an evaluation of the handover condition for the candidate target RAN nodes (e.g., target RAN node 1, target RAN node 2) and select a target RAN node for handover among the candidate target RAN nodes. For example, the UE may perform measurements on the candidate target RAN nodes, and determine whether a candidate target RAN node satisfies a handover condition for the candidate target RAN node among the candidate target RAN nodes based on a result of the measurements on the candidate target RAN nodes. If the UE identifies that the target RAN node 1 satisfies a handover condition for the target RAN node 1, the UE may select the target RAN node 1 as a target RAN node for the handover.

In step S1117, the UE may perform a random access to the selected target RAN node (e.g., target RAN node 1). For example, the UE may transmit a random access preamble to the target RAN node 1, and receive a random access response comprising an uplink grant from the target RAN node 1. If RACH-less handover is configured, the step S1117 may be omitted, and the uplink grant may be provided in step S1113. The uplink grant may be used for the UE to transmit a HO complete message to the target RAN node 1.

In step S1119, the UE may transmit a HO complete message to the target RAN node 1. When the UE has successfully accessed the target RAN node 1 (or, received uplink grant when RACH-less HO is configured), the UE may transmit a HO complete message comprising a C-RNTI to confirm the handover, along with uplink buffer status report, whenever possible, to the target RAN node 1 to indicate that the handover procedure is completed for the UE. The target RAN node 1 may verify the C-RNTI transmitted in the HO complete message.

Hereinafter, cell selection criterion is described.

The cell selection criterion S (or, simply S criterion/criteria) may be fulfilled if the equation “Srxlev>0 AND Squal>0” is satisfied. The Srxlev may be defined based on the equation Srxlev=Q_(rxlevmeas)−(Q_(rxlevmin)+Q_(rxlevminoffset))−P_(compensation)−Qoffset_(temp), and the Squal may be defined based on the equation Sqaul=Q_(qualmeas)−(Q_(qualmin)+Q_(qualminoffset))−Qoffset_(temp). Parameters related to the above stated equations may be defined as Table 5 below:

TABLE 5 Srxlev Cell selection RX level value (dB) Squal Cell selection quality value (dB) Qoffset_(temp) Offset temporarily applied to a cell (dB) Q_(rxlevmeas) Measured cell RX level value (RSRP) Q_(qualmeas) Measured cell quality value (RSRQ) Q_(rxlevmin) Minimum required RX level in the cell (dBm). If the UE supports SUL frequency for this cell, Qrxlevmin is obtained from q-RxLevMinSUL, if present, in SIB1, SIB2 and SIB4, additionally, if Q_(rxlevminoffsetcellSUL) is present in SIB3 and SIB4 for the concerned cell, this cell specific offset is added to the corresponding Qrxlevmin to achieve the required minimum RX level in the concerned cell; else Qrxlevmin is obtained from q-RxLevMin in SIB1, SIB2 and SIB4, additionally, if Q_(rxlevminoffsetcell) is present in SIB3 and SIB4 for the concerned cell, this cell specific offset is added to the corresponding Qrxlevmin to achieve the required minimum RX level in the concerned cell. Q_(qualmin) Minimum required quality level in the cell (dB). Additionally, if Q_(qualminoffsetcell) is signalled for the concerned cell, this cell specific offset is added to achieve the required minimum quality level in the concerned cell. Q_(rxlevminoffset) Offset to the signalled Q_(rxlevmin) taken into account in the Srxlev evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN. Q_(qualminoffset) Offset to the signalled Q_(qualmin) taken into account in the Squal evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN. P_(compensation) For FR1, if the UE supports the additionalPmax in the NR- NS-PmaxList, if present, in SIB1, SIB2 and SIB4: max(P_(EMAX1) − P_(PowerClass), 0) − (min(P_(EMAX2), P_(PowerClass)) − min(P_(EMAX1), P_(PowerClass))) (dB); else: max(P_(EMAX1) − P_(PowerClass), 0) (dB)For FR2, P_(compensation) is set to 0. P_(EMAX1), P_(EMAX2) Maximum TX power level of a UE may use when transmitting on the uplink in the cell (dBm). If UE supports SUL frequency for this cell, P_(EMAX1) and P_(EMAX2) are obtained from the p-Max for SUL in SIB1 and NR-NS-PmaxList for SUL respectively in SIB1, SIB2 and SIB4. else P_(EMAX1) and P_(EMAX2) are obtained from the p-Max and NR-NS-PmaxList respectively in SIB1, SIB2 and SIB4 for normal UL. P_(PowerClass) Maximum RF output power of the UE (dBm) according to the UE power class.

The signalled values Q_(rxlevminoffset) and Q_(qualminffset) may only be applied when a cell is evaluated for a cell selection as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN. During this periodic search for higher priority PLMN, the UE may check the S criteria of a cell using parameter values stored from a different cell of this higher priority PLMN.Hereinafter, cell reselection in multi-beam operations is described.

For cell reselection in multi-beam operations, a measurement quantity of a cell may be derived amongst beams corresponding to/associated with the cell based on SS/PBCH block as follows:

1> if nrofSS-BlocksToAverage is not configured in system information block (SIB) type 2 (SIB2); or

1> if absThreshSS-BlocksConsolidation is not configured in SIB2; or

1> if the highest beam measurement quantity value is below or equal to absThreshSS-BlocksConsolidation:

2> derive a cell measurement quantity as the highest beam measurement quantity value.

1>else:

2> derive a cell measurement quantity as the linear average of the power values of up to nrofSS-BlocksToAverage of highest beam measurement quantity values above absThreshSS-BlocksConsolidation.

The parameter nrofSS-BlocksToAverage may indicate the number of SSBs to average for a cell measurement derivation.

The parameter absThreshSS-BlocksConsolidation may indicate a threshold for a consolidation of layer 1 (L1) measurements per reference signal (RS) index and/or beam index.

Hereinafter, cell reselection criteria is described. The cell reselection criteria may comprise intra-frequency cell reselection criteria and/or inter-frequency cell reselection criteria with equal priority.

For the cell reselection criteria, cell-ranking criterion R (or, simply R criterion/criteria) may be used. The ranking value that is determined according to the cell-ranking criterion R may be referred to as R value.

The cell-ranking criterion R_(s) for serving cell may be defined by the equation R_(s)=Q_(meas),+Q_(hyst)_31 Qoffset_(temp), and the cell-ranking criterion R_(n) for neighboring cells may be defined by the R_(n)=Q_(meas,n)−Qoffset−Qoffset_(temp). Parameters related to the above stated equations may be defined as Table 6 below:

TABLE 6 Q_(meas) RSRP measurement quantity used in cell reselections. Qoffset For intra-frequency: Equals to Qoffset_(s, n), if Qoffset_(s, n) is valid, otherwise this equals to zero. For inter-frequency: Equals to Qoffset_(s, n) plus Qoffset_(frequency), if Qoffset_(s, n) is valid, otherwise this equals to Qoffset_(frequency). Qoffset_(temp) Offset temporarily applied to a cell.

The UE shall perform ranking of all cells that fulfil the cell selection criterion S. The cells shall be ranked according to the R criteria specified above by deriving Q_(meas,n) and Q_(meas), and calculating the R values using averaged RSRP results. If rangeToBestCell is not configured, the UE shall perform cell reselection to the highest ranked cell. In contrast, if rangeToBestCell is configured, then the UE shall perform cell reselection to the cell with the highest number of beams above the threshold (i.e., absThreshSS-BlocksConsolidation) among the cells whose R value is within rangeToBestCell of the R value of the highest ranked cell. If there are multiple such cells, the UE shall perform cell reselection to the highest ranked cell among them.

In all cases, the UE shall reselect the new cell, only if i)the new cell is better than the serving cell according to the cell reselection criteria specified above during a time interval Treselection_(RAT); and ii)more than 1 second has elapsed since the UE camped on the current serving cell.

As stated above, a UE may perform a cell reselection to a cell with the highest number of beams above the threshold (i.e., absThreshSS-BlocksConsolidation) among the cells whose R value is within rangeToBestCell of the R value of the highest ranked cell. In other words, the UE may perform a cell reselection to a cell with the highest number of good beams among the cells whose R value is within rangeToBestCell of the R value of the highest ranked cell. The reason why the number of good beams is taken into account is to select a robust cell from the UE perspective. However, different cells can be composed of/associated with different number of beams. So it is hard to say that the more good beams indicates the more robust cell.

Therefore, various embodiments of the present disclosure provide solutions that when a UE selects a target cell for a mobility in a multi-beam operation, the UE may select a cell with the highest proportion of beams above the beam quality threshold (or, simply beam-threshold which may comprise absThreshSS-BlocksConsolidation) among a set of the best candidate cells for the mobility—in other words, the UE may select a cell with the highest proportion of good beams among the set of the best candidate cells for the mobility. If there are multiple such cells, the UE may select the best quality cell among them (i.e., the cell whose cell quality is the highest).

FIG. 12 shows an example of a method for selecting a mobility target cell according to an embodiment of the present disclosure. The steps illustrated in FIG. 12 may be performed by a wireless device and/or a UE.

Referring to FIG. 12, in step S1201, the wireless device may perform measurements to derive a cell quality. The wireless device may perform measurements on neighbor cells around the wireless device, and may obtain a result of the measurements comprising the cell quality of each of the neighbor cells.

In step S1203, the wireless device may determine a set of candidate cells for a mobility based on the cell quality. The wireless device may determine a set of candidate cells for a mobility among the neighbor cells based on the cell quality of each of the neighbor cells.

In step S1205, the wireless device may select a mobility target cell from/among the set of candidate cells for the mobility based on a number of good beams and a number of detected beams. The detected beams may comprise total beams related with each of the candidate cells. The good beams may comprise beams whose beam quality is above a beam quality threshold among the total beams.

In step S1207, the wireless device may perform the mobility to the mobility target cell. For example, the wireless device may perform the mobility to the mobility target cell for which a good beam proportion is the highest among the candidate cells.

According to various embodiments, the beam quality threshold (e.g., absThreshSS-BlocksConsolidation) may be configured or signalled by a network to the wireless device via at least one of downlink control information (DCI), a media access control (MAC) control element (MAC CE), or a radio resource control (RRC) signalling.

According to various embodiments, the number of the total beams related with each candidate cell may be configured or signalled by a network to the wireless device via at least one of DCI, MAC CE, or RRC signalling.

According to various embodiments, the detected beams may comprise one or more beams that are detected by the wireless device for each candidate cell through a beam sweeping of each candidate cell. The good beams may comprise beams whose beam quality is above a beam quality threshold among the one or more beams. During a beam sweeping of a cell, a RAN node related with the cell may sweep all beams of the RAN node to transmit signals (e.g., reference signals such as SSB and/or CSI-RS) through the all beams of the RAN node.

According to various embodiments, the wireless device may select the mobility target cell among the set of candidate cells for the mobility based on a good beam proportion/ratio for each candidate cell. The good beam proportion for each candidate cell may comprise a proportion of the number of good beams related with each candidate cell to the number of detected beams related with each candidate cell.

According to various embodiments, the mobility target cell may be selected such that the good beam proportion for the mobility target cell is highest among the candidate cells.

According to various embodiments, the wireless device may perform measurements on a serving cell and neighbor cells to derive a cell quality of each neighbor cell and a cell quality of the serving cell. The cell quality of each neighbor cell is derived based on averaging beam qualities of beams related with each neighbor cell. The cell quality of the serving cell may be derived based on averaging beam qualities of beams related with the serving cell. The beams related with each neighbor cell may comprise total beams related with each neighbor cell, or beams that are detected by the wireless device for each neighbor cell through a beam sweeping of each neighbor cell. The beams related with the serving cell may comprise total beams related with the serving cell, or beams that are detected by the wireless device for the serving cell through a beam sweeping of the serving cell.

According to various embodiments, the wireless device may perform a ranking of a serving cell and neighbor cells based on the cell quality of each of the serving cell and neighbor cells to obtain a cell ranking of each of the serving cell and the neighbor cells. The wireless device may determine the set of candidate cells whose cell ranking is within a threshold range from a cell ranking of a highest ranked cell among the serving cell and the neighbor cells. The highest ranked cell may be a cell whose cell ranking is highest among the serving cell and the neighbor cells.

According to various embodiments, the threshold range (e.g., rangeToBestCell) may be configured or signalled by a network to the wireless device via at least one of DCI, MAC CE or RRC signalling.

According to various embodiments, the wireless device may perform measurements on neighbor cells to derive a cell quality of each neighbor cell. The wireless device may determine the set of candidate cells whose cell quality is within a threshold range from a cell quality of a best quality cell among the neighbor cells. The best quality cell may be a cell whose cell quality is best among the neighbor cells. The threshold range may be configured or signalled by a network to the wireless device via at least one of DCI, MAC CE or RRC signalling.

In various embodiments of the present disclosure, the proportion of beams above the beam-threshold (i.e., the proportion of good beams) may be used to determine a mobility target cell. The proportion of beams above the beam-threshold may be determined by a formula “the proportion of beams above the beam-threshold=the number of beams above the beam-threshold related with a cell (or, the number of good beams related with a cell)/the total number of beams that compose the cell”. The total number of beams that compose a cell may comprise the total number of beams related with the cell and/or the number of total beams related with the cell.

For a measurement of a target cell, the total number of beams that compose a cell can be configured or signalled by a network to the UE via DCI, MAC CE or RRC signalling. If the UE receives information for the total number of beams that compose a cell from the network, the UE may use the total number of beams related with the cell as a denominator in the above formula.

Alternatively, UE can estimate the total number of beams that compose a cell by detecting/measuring the cell. That is, if the UE detects N beams for a cell, then the UE can consider the cell is composed of N beams. In this case, the number of detected beams can be used as a denominator in the above formula.

UE may consider the cells whose cell quality (e.g., signal quality/signal strength/channel quality/channel state/RSRP/RSRQ/SINR of a cell) and/or cell ranking is within a threshold/threshold range of the cell quality of the best quality cell as the best candidate cells for the mobility.

Various embodiments of the present disclosure can be applied to all sorts of mobility (e.g., cell selection/re-selection, handover, PSCell/SCell addition/change, conditional mobility, conditional serving cell addition or change).

According to various embodiments of the present disclosure, a UE may perform measurements according to a network configuration (e.g., measurement configuration) and derive a cell quality from measurement results of multi-beams. For example, the cell quality may be derived by averaging the measurement results (e.g., beam quality) of M best beams or M good beams. The UE may identify a set of the best candidate cells for mobility based on the cell quality. The UE may consider the cells whose cell quality is within a threshold/threshold range of the cell quality of the best quality cell as the best candidate cells for the mobility. The UE may calculate the proportion of good beams for each cell included in the set of the best candidate cells. The UE may select a cell with the highest proportion of beams above the beam-threshold among the best candidate cells, as a target cell. Then, the UE may perform the mobility to the selected target cell.

FIG. 13 shows an example of a good beam proportion for each candidate cell according to an embodiment of the present disclosure.

When a UE performs a cell re-selection procedure, the UE may consider the cells whose R value is within a threshold1 of the R value of the highest ranked cell as candidate cells for cell re-selection.

For example, for cell re-selection, a UE may perform ranking of all cells that fulfil the cell selection criterion S. In FIG. 13, it is assumed that there are three cells whose R value is within the threshold1 of the R value of the highest ranked cell (i.e., cell A, B and C). Among the three cells, the highest ranked cell may be cell A. The UE may consider those cells as the best candidate cells for cell re-selection, so the UE may compare the proportion of good beams of those cells to select a mobility target cell. The cell A, B and C may be related with 4 beams, 8 beams and 16 beams, respectively. The number of beams above the beam-threshold (i.e., the number of good beams) for cell A, B and C may be one, three and four, respectively. Then, the proportion of good beams for cell A, B and C are ¼, ⅜ and 4/16(=¼), respectively, as shown in FIG. 13.

According to FIG. 13, the cell B is a cell with the highest proportion of beams above the beam-threshold among the best candidate cells for cell re-selection. Therefore, the UE may perform the cell re-selection to cell B.

In other words, if thresdhold1 (e.g., rangeToBestCell) is configured, the UE shall perform cell reselection to the cell with the highest proportion of beams above the beam-threshold (i.e., absThreshSS-BlocksConsolidation) among the cells whose R value is within rangeToBestCell of the R value of the highest ranked cell. If there are multiple such cells (i.e., if there are multiple cells having the same highest proportion of good beams), the UE shall perform cell reselection to the highest ranked cell among the multiple cells having the same highest proportion of good beams.

FIG. 14 shows an example of cell qualities of neighbour cells according to an embodiment of the present disclosure.

When UE performs a mobility (e.g., conditional handover), the UE may consider the cells whose cell quality (e.g., RSRP/RSRQ or SINR measurement result) is within a threshold2 of a cell quality of the best quality cell as candidate cells for mobility and/or handover.

For example, for a UE, the conditional handover may be configured, and the handover condition may be “Neighbour cell becomes better than threshold (e.g., event A4)”. The UE may acquire the measurement results of cell A, B, C, D and E, and the cell A, B, C, D and E may satisfy the mobility condition (i.e., the cell quality is higher than the threshold). The cell A may be the best quality cell (i.e., the cell A has the highest RSRP/RSRQ or SINR among the cell A, B, C, D and E. The cell quality of cell B and C may be within a threshold 2 of the cell quality of cell A, while the cell quality of cell D and E may not be within the threshold2, as show in FIG. 14.

Therefore, the UE may consider the cell A, B and C are candidate cells for handover. The cell A, B and C may be related with 4 beams, 8 beams and 16 beams, respectively. The number of beams above the beam-threshold for cell A, B and C may be one, three and four, respectively. Then, the proportion of good beams for cell A, B and C are ¼, ⅜ and 4/16(=¼), respectively. Cell B is the cell with the highest proportion of beams above the beam-threshold among the candidate cells for the mobility. Therefore, the UE may perform the handover to cell B.

In other words, if a threshold2 is configured, the UE shall perform a conditional mobility to the cell with the highest proportion of beams above the beam-threshold among the cells whose cell quality is within the threshold2 of the cell quality of the best quality cell. If there are multiple such cells (i.e., if there are multiple cells having the same highest proportion of good beams), the UE shall perform cell reselection/handover to the highest ranked cell or the best quality cell among the multiple cells having the same highest proportion of good beams.

FIG. 15 shows a UE to implement an embodiment of the present disclosure. The present disclosure described above for UE side may be applied to this embodiment.

A UE includes a processor 1510, a power management module 1511, a battery 1512, a display 1513, a keypad 1514, a subscriber identification module (SIM) card 1510, a memory 1520, a transceiver 1530, one or more antennas 1531, a speaker 1540, and a microphone 1541.

The processor 1510 may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of the radio interface protocol may be implemented in the processor 1510. The processor 1510 may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processing device. The processor 1510 may be an application processor (AP). The processor 1510 may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), a modem (modulator and demodulator). An example of the processor 1510 may be found in SNAPDRAGON™ series of processors made by Qualcomm®, EXYNOS™ series of processors made by Samsung®, A series of processors made by Apple®, HELIO™ series of processors made by MediaTek®, ATOM™ series of processors made by Intel® or a corresponding next generation processor.

The processor 1510 may be configured to, or configured to control the transceiver 1530 to implement steps performed by the UE and/or the wireless device throughout the disclosure.

The power management module 1511 manages power for the processor 1510 and/or the transceiver 1530. The battery 1512 supplies power to the power management module 1511. The display 1513 outputs results processed by the processor 1510. The keypad 1514 receives inputs to be used by the processor 1510. The keypad 1514 may be shown on the display 1513. The SIM card 1510 is an integrated circuit that is intended to securely store the international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephony devices (such as mobile phones and computers). It is also possible to store contact information on many SIM cards.

The memory 1520 is operatively coupled with the processor 1510 and stores a variety of information to operate the processor 1510. The memory 1520 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage device. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules can be stored in the memory 1520 and executed by the processor 1510. The memory 1520 can be implemented within the processor 1510 or external to the processor 1510 in which case those can be communicatively coupled to the processor 1510 via various means as is known in the art.

The transceiver 1530 is operatively coupled with the processor 1510, and transmits and/or receives a radio signal. The transceiver 1530 includes a transmitter and a receiver. The transceiver 1530 may include baseband circuitry to process radio frequency signals. The transceiver 1530 controls the one or more antennas 1531 to transmit and/or receive a radio signal.

The speaker 1540 outputs sound-related results processed by the processor 1510. The microphone 1541 receives sound-related inputs to be used by the processor 1510.

FIG. 16 shows another example of a wireless communication system to which the technical features of the present disclosure can be applied.

Referring to FIG. 16, the wireless communication system may include a first device 1610 (i.e., first device 210) and a second device 1620 (i.e., second device 220).

The first device 1610 may include at least one transceiver, such as a transceiver 1611, and at least one processing chip, such as a processing chip 1612. The processing chip 1612 may include at least one processor, such a processor 1613, and at least one memory, such as a memory 1614. The memory may be operably connectable to the processor 1613. The memory 1614 may store various types of information and/or instructions. The memory 1614 may store a software code 1615 which implements instructions that, when executed by the processor 1613, perform operations of the first device 910 described throughout the disclosure. For example, the software code 1615 may implement instructions that, when executed by the processor 1613, perform the functions, procedures, and/or methods of the first device 1610 described throughout the disclosure. For example, the software code 1615 may control the processor 1613 to perform one or more protocols. For example, the software code 1615 may control the processor 1613 to perform one or more layers of the radio interface protocol.

The second device 1620 may include at least one transceiver, such as a transceiver 1621, and at least one processing chip, such as a processing chip 1622. The processing chip 1622 may include at least one processor, such a processor 1623, and at least one memory, such as a memory 1624. The memory may be operably connectable to the processor 1623. The memory 1624 may store various types of information and/or instructions. The memory 1624 may store a software code 1625 which implements instructions that, when executed by the processor 1623, perform operations of the second device 1620 described throughout the disclosure. For example, the software code 1625 may implement instructions that, when executed by the processor 1623, perform the functions, procedures, and/or methods of the second device 1620 described throughout the disclosure. For example, the software code 1625 may control the processor 1623 to perform one or more protocols. For example, the software code 1625 may control the processor 1623 to perform one or more layers of the radio interface protocol.

The present disclosure may be applied to various future technologies, such as AI, robots, autonomous-driving/self-driving vehicles, and/or extended reality (XR).

<AI>

AI refers to artificial intelligence and/or the field of studying methodology for making it. Machine learning is a field of studying methodologies that define and solve various problems dealt with in AI. Machine learning may be defined as an algorithm that enhances the performance of a task through a steady experience with any task.

An artificial neural network (ANN) is a model used in machine learning. It can mean a whole model of problem-solving ability, consisting of artificial neurons (nodes) that form a network of synapses. An ANN can be defined by a connection pattern between neurons in different layers, a learning process for updating model parameters, and/or an activation function for generating an output value. An ANN may include an input layer, an output layer, and optionally one or more hidden layers. Each layer may contain one or more neurons, and an ANN may include a synapse that links neurons to neurons. In an ANN, each neuron can output a summation of the activation function for input signals, weights, and deflections input through the synapse. Model parameters are parameters determined through learning, including deflection of neurons and/or weights of synaptic connections. The hyper-parameter means a parameter to be set in the machine learning algorithm before learning, and includes a learning rate, a repetition number, a mini batch size, an initialization function, etc. The objective of the ANN learning can be seen as determining the model parameters that minimize the loss function. The loss function can be used as an index to determine optimal model parameters in learning process of ANN.

Machine learning can be divided into supervised learning, unsupervised learning, and reinforcement learning, depending on the learning method. Supervised learning is a method of learning ANN with labels given to learning data. Labels are the answers (or result values) that ANN must infer when learning data is input to ANN. Unsupervised learning can mean a method of learning ANN without labels given to learning data. Reinforcement learning can mean a learning method in which an agent defined in an environment learns to select a behavior and/or sequence of actions that maximizes cumulative compensation in each state.

Machine learning, which is implemented as a deep neural network (DNN) that includes multiple hidden layers among ANN, is also called deep learning. Deep learning is part of machine learning. In the following, machine learning is used to mean deep learning.

FIG. 17 shows an example of an AI device to which the technical features of the present disclosure can be applied.

The AI device 1700 may be implemented as a stationary device or a mobile device, such as a TV, a projector, a mobile phone, a smartphone, a desktop computer, a notebook, a digital broadcasting terminal, a PDA, a PMP, a navigation device, a tablet PC, a wearable device, a set-top box (STB), a digital multimedia broadcasting (DMB) receiver, a radio, a washing machine, a refrigerator, a digital signage, a robot, a vehicle, etc.

Referring to FIG. 17, the AI device 1700 may include a communication part 1710, an input part 1720, a learning processor 1730, a sensing part 1740, an output part 1750, a memory 1760, and a processor 1770.

The communication part 1710 can transmit and/or receive data to and/or from external devices such as the AI devices and the AI server using wire and/or wireless communication technology. For example, the communication part 1710 can transmit and/or receive sensor information, a user input, a learning model, and a control signal with external devices. The communication technology used by the communication part 1710 may include a global system for mobile communication (GSM), a code division multiple access (CDMA), an LTE/LTE-A, a 5G, a WLAN, a Wi-Fi, Bluetooth™, radio frequency identification (RFID), infrared data association (IrDA), ZigBee, and/or near field communication (NFC).

The input part 1720 can acquire various kinds of data. The input part 1720 may include a camera for inputting a video signal, a microphone for receiving an audio signal, and a user input part for receiving information from a user. A camera and/or a microphone may be treated as a sensor, and a signal obtained from a camera and/or a microphone may be referred to as sensing data and/or sensor information. The input part 1720 can acquire input data to be used when acquiring an output using learning data and a learning model for model learning. The input part 1720 may obtain raw input data, in which case the processor 1770 or the learning processor 1730 may extract input features by preprocessing the input data.

The learning processor 1730 may learn a model composed of an ANN using learning data. The learned ANN can be referred to as a learning model. The learning model can be used to infer result values for new input data rather than learning data, and the inferred values can be used as a basis for determining which actions to perform. The learning processor 1730 may perform AI processing together with the learning processor of the AI server. The learning processor 1730 may include a memory integrated and/or implemented in the AI device 1700. Alternatively, the learning processor 1730 may be implemented using the memory 1760, an external memory directly coupled to the AI device 1700, and/or a memory maintained in an external device.

The sensing part 1740 may acquire at least one of internal information of the AI device 1700, environment information of the AI device 1700, and/or the user information using various sensors. The sensors included in the sensing part 1740 may include a proximity sensor, an illuminance sensor, an acceleration sensor, a magnetic sensor, a gyro sensor, an inertial sensor, an RGB sensor, an IR sensor, a fingerprint recognition sensor, an ultrasonic sensor, an optical sensor, a microphone, a light detection and ranging (LIDAR), and/or a radar.

The output part 1750 may generate an output related to visual, auditory, tactile, etc. The output part 1750 may include a display unit for outputting visual information, a speaker for outputting auditory information, and/or a haptic module for outputting tactile information.

The memory 1760 may store data that supports various functions of the AI device 1700. For example, the memory 1760 may store input data acquired by the input part 1720, learning data, a learning model, a learning history, etc.

The processor 1770 may determine at least one executable operation of the AI device 1700 based on information determined and/or generated using a data analysis algorithm and/or a machine learning algorithm. The processor 1770 may then control the components of the AI device 1700 to perform the determined operation. The processor 1770 may request, retrieve, receive, and/or utilize data in the learning processor 1730 and/or the memory 1760, and may control the components of the AI device 1700 to execute the predicted operation and/or the operation determined to be desirable among the at least one executable operation. The processor 1770 may generate a control signal for controlling the external device, and may transmit the generated control signal to the external device, when the external device needs to be linked to perform the determined operation. The processor 1770 may obtain the intention information for the user input and determine the user's requirements based on the obtained intention information. The processor 1770 may use at least one of a speech-to-text (STT) engine for converting speech input into a text string and/or a natural language processing (NLP) engine for acquiring intention information of a natural language, to obtain the intention information corresponding to the user input. At least one of the STT engine and/or the NLP engine may be configured as an ANN, at least a part of which is learned according to a machine learning algorithm. At least one of the STT engine and/or the NLP engine may be learned by the learning processor 1730 and/or learned by the learning processor of the AI server, and/or learned by their distributed processing. The processor 1770 may collect history information including the operation contents of the AI device 1700 and/or the user's feedback on the operation, etc. The processor 1770 may store the collected history information in the memory 1760 and/or the learning processor 1730, and/or transmit to an external device such as the AI server. The collected history information can be used to update the learning model. The processor 1770 may control at least some of the components of AI device 1700 to drive an application program stored in memory 1760. Furthermore, the processor 1770 may operate two or more of the components included in the AI device 1700 in combination with each other for driving the application program.

FIG. 18 shows an example of an AI system to which the technical features of the present disclosure can be applied.

Referring to FIG. 18, in the AI system, at least one of an AI server 1820, a robot 1810 a, an autonomous vehicle 1810 b, an XR device 1810 c, a smartphone 1810 d and/or a home appliance 1810 e is connected to a cloud network 1800. The robot 1810 a, the autonomous vehicle 1810 b, the XR device 1810 c, the smartphone 1810 d, and/or the home appliance 1810 e to which the AI technology is applied may be referred to as AI devices 1810 a to 1810 e.

The cloud network 1800 may refer to a network that forms part of a cloud computing infrastructure and/or resides in a cloud computing infrastructure. The cloud network 1800 may be configured using a 3G network, a 4G or LTE network, and/or a 5G network. That is, each of the devices 1810 a to 1810 e and 1820 consisting the AI system may be connected to each other through the cloud network 1800. In particular, each of the devices 1810 a to 1810 e and 1820 may communicate with each other through a base station, but may directly communicate with each other without using a base station.

The AI server 1820 may include a server for performing AI processing and a server for performing operations on big data. The AI server 1820 is connected to at least one or more of AI devices constituting the AI system, i.e. the robot 1810 a, the autonomous vehicle 1810 b, the XR device 1810 c, the smartphone 1810 d and/or the home appliance 1810 e through the cloud network 1800, and may assist at least some AI processing of the connected AI devices 1810 a to 1810 e. The AI server 1820 can learn the ANN according to the machine learning algorithm on behalf of the AI devices 1810 a to 1810 e, and can directly store the learning models and/or transmit them to the AI devices 1810 a to 1810 e. The AI server 1820 may receive the input data from the AI devices 1810 a to 1810 e, infer the result value with respect to the received input data using the learning model, generate a response and/or a control command based on the inferred result value, and transmit the generated data to the AI devices 1810 a to 1810 e. Alternatively, the AI devices 1810 a to 1810 e may directly infer a result value for the input data using a learning model, and generate a response and/or a control command based on the inferred result value.

Various embodiments of the AI devices 1810 a to 1810 e to which the technical features of the present disclosure can be applied will be described. The AI devices 1810 a to 1810 e shown in FIG. 18 can be seen as specific embodiments of the AI device 1700 shown in FIG. 17.

The present disclosure can have various advantageous effects.

For example, a UE may consider a proportion of good beams instead of the number of good beams when the UE selects a mobility target cell among candidate cells for a mobility so that the UE can select more robust cell from a UE perspective. By selecting more robust cell, a rate of a mobility success can be increased and a signalling overhead caused by an unnecessary mobility can be avoided.

Advantageous effects which can be obtained through specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there may be a variety of technical effects that a person having ordinary skill in the related art can understand and/or derive from the present disclosure. Accordingly, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that may be understood or derived from the technical features of the present disclosure.

In view of the exemplary systems described herein, methodologies that may be implemented in accordance with the disclosed subject matter have been described with reference to several flow diagrams. While for purposed of simplicity, the methodologies are shown and described as a series of steps or blocks, it is to be understood and appreciated that the claimed subject matter is not limited by the order of the steps or blocks, as some steps may occur in different orders or concurrently with other steps from what is depicted and described herein. Moreover, one skilled in the art would understand that the steps illustrated in the flow diagram are not exclusive and other steps may be included or one or more of the steps in the example flow diagram may be deleted without affecting the scope of the present disclosure.

Claims in the present description can be combined in a various way. For instance, technical features in method claims of the present description can be combined to be implemented or performed in an apparatus, and technical features in apparatus claims can be combined to be implemented or performed in a method. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in an apparatus. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in a method. Other implementations are within the scope of the following claims. 

What is claimed is:
 1. A method performed by a wireless device in a wireless communication system, the method comprising: performing measurements to derive a cell quality; determining a set of candidate cells for a mobility based on the cell quality; selecting a mobility target cell from the set of candidate cells for the mobility based on a number of good beams and a number of detected beams; and performing the mobility to the mobility target cell.
 2. The method of claim 1, wherein the detected beams comprise total beams related with each candidate cell, and wherein the good beams comprise beams whose beam quality is above a beam quality threshold among the total beams.
 3. The method of claim 2, wherein the beam quality threshold is configured or signalled by a network to the wireless device via at least one of downlink control information (DCI), a media access control (MAC) control element (MAC CE), or a radio resource control (RRC) signalling.
 4. The method of claim 2, wherein a number of the total beams related with each candidate cell is configured or signalled by a network to the wireless device via at least one of downlink control information (DCI), a media access control (MAC) control element (MAC CE), or a radio resource control (RRC) signalling.
 5. The method of claim 1, wherein the detected beams comprise one or more beams that are detected by the wireless device for each candidate cell through a beam sweeping of each candidate cell, and wherein the good beams comprise beams whose beam quality is above a beam quality threshold among the one or more beams.
 6. The method of claim 1, wherein the selecting of the mobility target cell comprises selecting the mobility target cell among the set of candidate cells for the mobility based on a good beam proportion for each candidate cell, and wherein the good beam proportion for each candidate cell comprises a proportion of the number of good beams related with each candidate cell to the number of detected beams related with each candidate cell.
 7. The method of claim 6, wherein the mobility target cell is selected such that the good beam proportion for the mobility target cell is highest among the candidate cells.
 8. The method of claim 1, wherein the performing of the measurements comprises performing measurements on a serving cell and neighbor cells to derive a cell quality of each neighbor cell and a cell quality of the serving cell, wherein the cell quality of each neighbor cell is derived based on averaging beam qualities of beams related with each neighbor cell, and wherein the cell quality of the serving cell is derived based on averaging beam qualities of beams related with the serving cell.
 9. The method of claim 1, wherein the determining of the set of candidate cells comprises: performing a ranking of a serving cell and neighbor cells based on the cell quality of each of the serving cell and the neighbor cells to obtain a cell ranking of each of the serving cell and the neighbor cells; and determining the set of candidate cells whose cell ranking is within a threshold range from a cell ranking of a highest ranked cell among the serving cell and the neighbor cells, wherein the highest ranked cell is a cell whose cell ranking is highest among the serving cell and the neighbor cells.
 10. The method of claim 9, wherein the threshold range is configured or signalled by a network to the wireless device via at least one of downlink control information (DCI), a media access control (MAC) control element (MAC CE), or a radio resource control (RRC) signalling.
 11. The method of claim 1, wherein the performing of the measurements comprises performing measurements on neighbor cells to derive a cell quality of each neighbor cell, and wherein the determining of the set of candidate cells comprises determining the set of candidate cells whose cell quality is within a threshold range from a cell quality of a best quality cell among the neighbor cells, and wherein the best quality cell is a cell whose cell quality is best among the neighbor cells.
 12. The method of claim 1, wherein the wireless device is in communication with at least one of a user equipment, a network, or autonomous vehicles other than the wireless device.
 13. A wireless device in a wireless communication system comprising: a transceiver; a memory; and at least one processor operatively coupled to the transceiver and the memory, and configured to: perform measurements to derive a cell quality, determine a set of candidate cells for a mobility based on the cell quality, select a mobility target cell from the set of candidate cells for the mobility based on a number of good beams and a number of detected beams, and performing the mobility to the mobility target cell.
 14. A processor for a wireless device in a wireless communication system, wherein the processor is configured to control the wireless device to perform operations comprising: performing measurements to derive a cell quality; determining a set of candidate cells for a mobility based on the cell quality; selecting a mobility target cell from the set of candidate cells for the mobility based on a number of good beams and a number of detected beams; and performing the mobility to the mobility target cell.
 15. A computer-readable medium having recorded thereon a program for performing each step of a method on a computer, the method comprising: performing measurements to derive a cell quality; determining a set of candidate cells for a mobility based on the cell quality; selecting a mobility target cell from the set of candidate cells for the mobility based on a number of good beams and a number of detected beams; and performing the mobility to the mobility target cell. 